Clarification about model registry

Author: crmne

CONTRIBUTING.md

@@ -70,6 +70,10 @@ If you're adding a new provider:
 5. **Update aliases.json** - Add entries to aliases.json for models accessible through your provider
 6. **Implement refresh mechanism** - Ensure your provider supports the `list_models` method for refreshing
 
+### Model Registry (`models.json`)
+
+The `models.json` file is autogenerated. PRs shouldn't change the file manually, instead either refresh it with `rake models:update` or change the relevant `capabilities.rb` files and then refresh it.
+
 ### Model Aliases
 
 For providers that use complex model identifiers (like Bedrock's `anthropic.claude-3-5-sonnet-20241022-v2:0:200k`), add mappings to the global aliases.json file:
@@ -200,4 +204,4 @@ Gem versioning follows [Semantic Versioning](https://semver.org/):
 
 Releases are handled by the maintainers through the CI/CD pipeline.
 
-Thanks for helping make RubyLLM better!
+Thanks for helping make RubyLLM better!